Astrebla spp.


Scientific name

Astrebla elymoides F. Muell. ex F.M. Bailey
Astrebla lappacea (Lindl.) Domin
Astrebla pectinata (Lindl.) F. Muell.
Astrebla squarrosa C.E. Hubb.

Subordinate taxa:
Astrebla pectinata (Lindl.) F. Muell. var. curvifolia F.M. Bailey

Synonyms

For A. lappacea:
Astrebla triticoides (Lindl.) F. Muell.
Danthonia lappacea Lindl.
Danthonia triticoides Lindl.

For A. pectinata:
Danthonia pectinata Lindl.

Family/tribe

Family: Poaceae (alt. Gramineae) subfamily: Chloridoideae tribe: Cynodonteae.

Common names

hoop Mitchell grass (A. elymoides)
curly Mitchell grass (A. lappacea)
barley Mitchell grass (A. pectinata)
bull Mitchell grass (A. squarrosa)

Morphological description

Tussocky perennial grasses growing to 1 m tall.  The species have different morphology.  Hoop Mitchell has long, narrow weeping seed heads whereas bull Mitchell seed heads are coarse, 10–14 cm long, with distinct hooks on the end of each awn, and may stand to 1.5 m.  The seed head of barley Mitchell has two distinct, closely packed rows of seeds and curly Mitchell’s bristly seed heads are usually held within the grass foliage.
The root system consists of short stout branched rhizomes from which numerous wiry roots spread outwards and then vertically down through the blocky clay soil.

Distribution

Native to:
Australasia:  Australia – New South Wales, Northern Territory, Queensland, South Australia, Western Australia.
Native of heavy clay soils of the downs in the arid zone of much of northern and central Australia.

Uses/applications

Native pastures, but seed has been harvested to restore Mitchell grasslands after cropping.
During the cool dry season, Mitchell grass acts as standing hay preserved by the dry atmosphere and absence of rainfall .  Winter rain is not at all unusual in southern Astrebla grasslands.  Light rain allows fungal attack, blackening of the dry leaf and deterioration of nutritive value.

Ecology

Soil requirements

Cracking clay soils, usually with high pH and free limestone.  Some tolerance to salinity.

Moisture

Top

Best development occurs in areas receiving between 250 and 550 mm annual rainfall .
Extremely drought -tolerant due to their robust root system;  however, many plants die in extremely dry periods, e.g. in Australia in 1930’s, 1960’s and early 2000’s.
Hoop Mitchell is found on wetter depressions, the coarse bull Mitchell is dominant in seasonally flooded country usually in northern Australia, barley Mitchell is common in more arid areas where soils do not crack as severely and curly Mitchell is more common in eastern Mitchell grass downs of Queensland.

Temperature

Warm season growth, up to 1,000 m asl.  Growth has usually ceased before frosts are experienced because summer soil moisture is usually exhausted.  Some growth response to heavier winter rainfall .

Light

Open sunlight.

Reproductive development

Flowering is independent of photoperiod;  they can flower at almost any time of the year in response to rainfall .

Defoliation

The robust root system makes Mitchell grass resistant to heavy grazing.  Tussocks are vulnerable to heavy grazing during prolonged drought .  Large scale seedling recruitment is rare.

Fire

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Mitchell grass is rarely burned, being too valuable as a reserve of feed in an arid climate.  However, it will recover well from fire in the absence of grazing following rain.

Agronomy

Establishment

Seed can be sown into a seedbed or oversown and trampled in by livestock during wet weather.

Fertiliser

No information available.

Compatibility (with other species)

Robust tussocks growing in an arid zone result in strong competition, but the inter tussock spaces may be occupeied by other grasses (perennial species Aristida spp., Dichanthium spp.and annual species of Iseilema, Dactyloctenium and Panicum).  Some native legumes (e.g. Glycine spp. and Indigofera spp.) co-exist and a large range of C4 dicotyledoneous species.
Winter rainfall in more southerly regions results in growth of a wide range of C3 forbs.

Companion species

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In the higher latitudes with more winter rainfall , Medicago spp. have naturalised.

Pests and diseases

No information available.

Ability to spread

Large scale seedling recruitment is rare but localised spread does occur when seed is present.

Weed potential

Low.

Feeding value

Nutritive value

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Moderate nutritional value, often limited by low soil nitrogen after a wet year.

Palatability/acceptability

Mitchell grasses are not particularly palatable during the wet season.  Livestock preferentially select other accompanying species during the summer growing period.  However, the Mitchell grasses retain their leaf during the dry season and are eaten then (there being little other feed).

Toxicity

A fungus (Corallocytostroma spp.) sometimes found on the stems of Mitchell grass in the Kimberley Region of northern Western Australia has caused ‘black soil blindness’.  Up to 5% of stock grazing affected Mitchell grass may die.  The fungus is a hard rough body about 10–20 mm diameter and grows on the grass stem at a node or axillary shoot.

Production potential

Dry matter

Yields of 2,000 kg/ha are common in well grazed pastures during good seasons.

Animal production

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Highly variable depending on rainfall .

Genetics/breeding

Does not out cross to any great extent.

Seed production

Natural stands of Mitchell grasses produce abundant seed heads that can be harvested by direct heading.

Herbicide effects

No information available.

Strengths

  • Very drought tolerant.
  • Grow well on heavy cracking clay soils.
  • Good stand-over feed.

Limitations

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  • Not very palatable.

Other comments

   

Selected references

Milson, J.M. (2000) Pasture plants of north-west Queensland. Dept Primary Industries, Queensland, Brisbane, Australia. Information Series QI00015.
Orr, D.M. (1975) A review of Astrebla (Mitchell grass ) pastures in Australia. Tropical Grasslands, 9, 21–35.
Orr, D.M. and Holmes, W.E. (1984) Mitchell grasslands. In: Harrington, G.N., Wilson, A.D. and Young, M.D. (eds) Management of Australia’s Rangelands. (CSIRO, Melbourne).
Partridge I.J. (1996) Managing Mitchell grass : a grazier’s guide. Dept Primary Industries, Queensland, Brisbane, Australia. Information Series QI96009.
Jubb, T.F., Main, D.C., Mitchell, R.G., Shivas, R.G. and De Witte, K.W. (1996) Black soil blindness: a new mycotoxicosis of cattle grazing Corallocytostroma-infected Mitchell grass (Astrebla spp). Australian Veterinary Journal, 73, 49–51.

Internet links

Cultivars

Cultivars

Country/date released

Details

'Yanda'
(A. lappacea)

Australia (1996) Selected for improved cool season green leaf growth, dry matter production and a high proportion of warm season leaf production.

'Turanti'
(A. pectinata)

Australia (1996) Selected for improved cool season green leaf growth, dry matter production and a high proportion of warm season leaf production.

Promising accessions

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Promising accessions

Country

Details

None reported.